Semiconductor integrated circuits and other microelectronic devices typically include a substrate or workpiece, such as a silicon wafer, and one or more metal layers disposed on the workpiece. The metal layers are typically used to interconnect components of the integrated circuit. Metal layers may also define devices such as read/write heads, micro electrical-mechanical devices, and other microelectronic structures. The metal layers can be formed from metals such as nickel, tungsten, solder, platinum, and copper. The metal layers can be formed on the workpiece with techniques such as chemical vapor deposition (CVD), physical vapor deposition (PVD), electroplating, and electroless plating.
In one electrochemical plating process, a very thin seed layer of metal is applied to the workpiece using physical or chemical vapor deposition and is deposited to a thickness of approximately 1,000 angstroms. An electrical current is applied to the seed layer while the workpiece is immersed in an electrochemical processing fluid to form a thicker blanket layer on the seed layer. The blanket layer can have a thickness of layer while the workpiece is immersed in an electrochemical processing fluid to form a thicker blanket layer on the seed layer. The blanket layer can have a thickness of approximately 6,000 to 15,000 angstroms and can fill trenches, vias and other apertures in the workpiece to provide electrically conductive features within the apertures. After the blanket layer has been electroplated onto the workpiece, excess metal material can be removed (for example, using chemical-mechanical planarization) and subsequent structures can then be disposed on the resulting metal layer.
FIG. 1 is a cross-sectional side elevational view of a conventional apparatus 10 for electroplating a microelectronic workpiece 23. The apparatus 10 includes a cup 12 supplied with electrochemical processing fluid via a supply tube 16. The supply tube 16 also supports a positively charged anode 13. The cup 12 includes sidewalls 17 having an upper edge 18 that defines a free surface 19 of the processing fluid. The processing fluid flows through the supply tube 16, into the cup 12 and over the sidewalls 17 into an overflow vessel 11, as indicated by arrows “S.” The fluid can be removed from the bottom of the overflow vessel 11 for disposal or recirculation.
A reactor head 20 supports the microelectronic workpiece 23 relative to the processing fluid in the cup 12 and is movable relative to the cup 12 and the overflow vessel 11 between a closed position (shown in FIG. 1) with the workpiece 23 in contact with the processing fluid, and an open position. The reactor head 20 includes a workpiece support or rotor 21 that supports the microelectronic workpiece 23 in a face-down orientation. The support 21 includes a contact assembly 22 having a plurality of electrical contact points 27 that can be removably coupled to a conductive surface (such as a seed layer) of the microelectronic workpiece 23. A backing plate 4 biases the workpiece 23 into engagement with the contact points 27 and is moveable relative to the workpiece 23 between an engaged position (shown in solid lines in FIG. 1) and a disengaged position (shown in broken lines in FIG. 1). A bellows seal 3 surrounds the backing plate 4. The support 21 is rotatably coupled to the reactor head 20 with a shaft 30 connected to a motor 24. Accordingly, the support 21 and the workpiece 23 can rotate relative to the reactor head 20 and the cup 12 (as indicated by arrows “R”) while a negative electrical charge is applied to the electrical contact points 27 to attract conductive ions in the processing fluid to the conductive surface of the workpiece 23.
In one aspect of the conventional arrangement shown in FIG. 1, electrical power is transmitted from the non-rotating reactor head 20 to the rotating microelectronic workpiece 23 via a rotating electrical connection. For example, as shown in FIG. 2, the shaft 30 can include a conductor 31 connected at a lower end to the contact assembly 22 (FIG. 1) and connected at an upper end to a rotary contact 60 that rotates with the shaft 30. The reactor head 20 (FIG. 1) can support a fixed contact 70 that is connected with a cable 34 to a power source (not shown). Accordingly, the shaft 30 and the rotary contact 60 rotate relative to the fixed contact 70 while maintaining electrical contact with the fixed contact 70 and the microelectronic workpiece 23.
In another conventional arrangement, it may be advantageous to purge oxygen from a region proximate to the junction between the microelectronic workpiece 23 (FIG. 1) and the contact assembly 22, for example, to minimize etching of the seed layer and/or reduce the likelihood for oxidizing the seed layer. Accordingly, the apparatus 10 (FIG. 1) can include a purge fluid pathway that provides purge fluid to the support 21 via the shaft 30. In one aspect of this arrangement (shown in FIG. 3), the shaft 30 can include a fluid channel 41 having an entrance port 45 at one end and an exit port 44 at the opposite end. The entrance port 45 extends through the rotary contact 60 and aligns with an axial supply passage 71 extending through the fixed contact 70. The fixed contact 70 also includes a fluid connector 72 for coupling to a source of purge fluid (not shown). Accordingly, the purge fluid can be supplied to the fluid connector 72, through the fixed contact 70, through the rotary contact 60, and through the shaft 30 to the junction region between the microelectronic workpiece 23 and the contact assembly 22.